JP2017129887A - Polarization element and manufacturing method of polarization element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization element that can provide a desired polarization property and has good transmissivity.SOLUTION: A polarization element includes a substrate transparent to light from a usage band, and a grid pattern made of translucent material in which a plurality of convex parts continuously arranged in a single direction in a plane of the substrate are formed on a surface of the substrate at a pitch smaller than wavelength of the light from the usage band. The convex part comprises a base having a rectangular cross section, and a tapered surface part formed at a leading end of the base. A fine particle layer made of inorganic material is laminated on at least one surface of the tapered surface part, and the fine particle layer does not protrude from a side face of the base.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing element typified by a polarizing plate and a polarizing filter, and a method for manufacturing the polarizing element.

  In a liquid crystal display device, particularly a transmissive liquid crystal display device, it is indispensable to dispose a polarizing plate on the surface of the liquid crystal panel from the principle of image formation. In recent years, liquid crystal display devices have been promoted with high brightness and downsizing, and accordingly, high heat resistance and light resistance are also required for polarizing plates. For example, in the case of a liquid crystal display device that uses a light source with a large amount of light, such as a transmissive liquid crystal projector, the polarizing plate receives strong radiation. Therefore, the heat resistance required for the polarizing plate used for these is required.

  A conventional polarizing plate using an organic film has insufficient heat resistance and light resistance, and it has been confirmed that polarization characteristics are significantly deteriorated against strong radiant heat from a high brightness light source. On the other hand, a wire grid type polarizing plate made of a fine metal grid has been proposed. A wire grid type polarizing plate is formed by forming a plurality of fine metal wires in a lattice pattern on a substrate, and absorbs or reflects a polarized light component parallel to the fine metal wire, and transmits a polarized light component orthogonal to the fine metal wire. The polarization characteristics of

  In the metal fine grid, a metal film such as aluminum is formed on a substrate by sputtering or vapor deposition, and a high-density fine resist pattern is formed on the metal film by a photolithography technique such as interference exposure. However, when the high density fine resist pattern is exposed, reflected interference light from the surface of the metal film is generated, so that the resist pattern shape is not a simple rectangle, but the width is locally narrowed in the height direction. . As a countermeasure, the constriction is reduced by applying an antireflection film (BARC) under the resist layer. However, the constriction cannot be completely suppressed.

  When the constriction occurs in the resist pattern, the resist pattern easily falls, and when the pattern falls, the resist pattern is not resolved, and therefore the pattern collapse leads to deterioration of resolution. In other words, if the resist pattern is tilted, it cannot be a processed mask at all, and desired polarization characteristics cannot be obtained.

  In addition, the effect of the constriction of the resist pattern is not only a problem of pattern collapse, but also when the resist pattern is used as a mask during dry etching, it causes process instability such as fluctuation of the etching rate, resulting in poor productivity and manufacturing. Costs also increase.

JP 2007-148344 A

For such a problem, a pattern forming layer is provided with a material transparent to visible light such as SiO2 on a substrate transparent to visible light, and after forming a lattice-shaped uneven portion, the substrate is inclined with respect to the substrate surface. A polarizing element has been proposed in which an inorganic fine particle layer made of an aluminum-based material or a semiconductor material is provided on the top of the uneven portion or at least one side surface thereof from the direction (see Patent Document 1). According to this polarizing plate, an uneven portion having a texture structure is formed by lapping, rubbing or mold transfer technology using an abrasive sheet, and therefore, an inorganic fine particle layer having a desired fine shape can be formed without performing pattern etching. it can.

  However, depending on the shape of the concavo-convex portion, as shown in FIG. 8, when the metal fine particles 51 are attached to the surface of the substrate 50 from an oblique direction, the metal fine particles 51 approach the space 53 between the convex portions 52. As a result, the transmittance of the light L is lowered. This tendency becomes more prominent as the lattice pattern becomes finer. In the polarizing element, the transmittance is an important factor for evaluating characteristics as well as the contrast. Therefore, a polarizing element that forms a desired lattice pattern and does not impair the transmittance is desired.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a polarizing element capable of obtaining desired polarization characteristics in the visible light region and having good light transmittance and a method for manufacturing the same.

  In order to solve the above-described problems, a polarizing element according to the present invention includes a substrate transparent to light in a use band, and a convex portion continuous in one direction in the plane of the substrate on the substrate surface. A plurality of grid patterns made of a translucent material formed at a pitch smaller than the wavelength of light, and the convex portion includes a base portion having a rectangular cross section and a tapered surface portion formed at the tip of the base portion. Thus, a fine particle layer made of an inorganic material is laminated on at least one surface of the tapered surface portion, and the fine particle layer does not protrude beyond the side surface of the base portion.

  Further, the manufacturing method of the polarizing element according to the present invention includes a translucent substrate, a base portion having a rectangular cross section that is continuous in one in-plane direction of the translucent substrate, and a tapered surface portion formed at the tip of the base portion. And a step of forming a grid pattern in which a plurality of convex portions are formed at a pitch smaller than the wavelength of light in the use band, and inorganic fine particles are laminated on the tapered surface portion from an oblique direction so as to protrude beyond the side surface of the base portion. Forming a fine particle layer.

  According to the present invention, in the polarizing element, the fine particle layer laminated on the convex portion constituting the grid pattern is deposited on the tapered surface portion and does not protrude from the side surface of the base portion. That is, since the fine particle layer does not protrude between the convex portions in the grid pattern, the light transmitted between the convex portions is not blocked, and the transmittance of the substrate can be maintained high.

  In addition, since the polarizing element is directly provided with a grid pattern without providing a metal film on the substrate, there is no occurrence of pattern collapse or constriction even if a resist pattern is formed by photolithography technology such as interference exposure. Thus, a fine grid pattern can be formed with high accuracy by etching.

  Furthermore, the polarizing element forms a convex portion having a base portion and a tapered surface portion provided on the upper surface of the base portion by switching between isotropic etching and anisotropic etching. The convex portion has a predetermined height by providing a base. Therefore, the polarizing element can form a grid pattern having high contrast.

It is a figure which shows the polarizing element to which this invention was applied, (a) is sectional drawing, (b) is a top view. It is sectional drawing which shows the convex part of the grid pattern 3, (a) is a figure before lamination | stacking of a fine particle layer, (b) is a figure which shows after lamination | stacking of a fine particle layer. It is a figure which shows the manufacturing process of the polarizing element to which this invention was applied. It is a figure which shows the lamination | stacking method of a fine particle layer. It is a graph which shows the relationship between the height T and the lower part width W1 of the convex part of a grid pattern, and the average transmittance | permeability of the light of the 530-580 nm band of a polarizing element. It is a graph which shows the relationship between the average transmittance | permeability of the light of a 530-580 nm band of a polarizing element, and the pitch P of the lower part width W1 / convex part of a convex part. 4 is a graph showing the relationship between the average transmittance of light in the 530 to 580 nm band of the polarizing element and the angle A of the tapered surface portion 10b of the convex portion 10; It is a SEM image which shows a grid pattern. It is sectional drawing which shows the grid pattern which formed the fine particle layer in the conventional uneven | corrugated | grooved part.

  Hereinafter, a polarizing element to which the present invention is applied and a method for manufacturing the polarizing element will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention. Further, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Configuration of Polarizing Element 1]
As shown in FIG. 1A and FIG. 1B, a polarizing element 1 to which the present invention is applied includes a substrate 2 that is transparent to light in a use band, and a transparent material on the surface of the substrate 2. It has the formed grid pattern 3 and the fine particle layer 4 made of an inorganic material formed on the upper surface of the convex portion 10 of the grid pattern 3. The polarizing element 1 is a resonance absorption type that uses the difference in optical absorptance due to the optical anisotropy in the in-plane axial direction of the island-shaped inorganic fine particles formed on the substrate 2 to make the desired polarization characteristics appear. It is an inorganic polarizing element.

  The substrate 2 can be used in any band, for example, an inorganic material or an organic material that is transparent to visible light, but is preferably made of glass or a ceramic material because heat resistance is increased. Further, by using a material having high thermal conductivity such as quartz or sapphire, heat dissipation can be improved and heat resistance can be improved. In the present embodiment, glass, particularly quartz is preferably used as the substrate 2.

  The grid pattern 3 is formed in a predetermined lattice shape by performing fine processing such as etching on the surface of the substrate 2. The grid pattern 3 forms an underlayer of the fine particle layer 4, and the optical characteristics of the polarizing element 1 depending on the shape of the fine particle layer 4 are determined by the processing size and pattern shape of the grid pattern 3. The grid pattern 3 is formed in a lattice shape, thereby imparting shape anisotropy to the fine particle layer 4 formed on the upper surface of the convex portion 10.

  The grid pattern 3 has a pitch that is smaller than the wavelength of the light in the band of use, with the convex portions 10 continuing in one direction in the plane of the substrate 2, in FIG. It is configured by forming a plurality over the direction. As shown in FIG. 2, the convex portion 10 is formed in a substantially rectangular base portion 10 a and the tip of the base portion 10 a in a cross-sectional view in the arrow X direction in FIG. The fine particle layer 4 made of an inorganic material is laminated on at least one surface of the tapered surface portion 10b.

  In the polarizing element 1, the inorganic fine particles are distributed in the form of islands on the surface of the substrate 2 by forming the fine particle layer 4 on the tapered surface portion 10 b of the convex portion 10. The fine particle layer 4 is made of, for example, aluminum fine particles, and is formed by an ion beam sputtering method in which a film is formed obliquely with respect to the surface of the substrate 2 as will be described later. Thereby, in the fine particle layer 4, aluminum fine particles are laminated on at least one surface of the tapered surface portion 10b of the convex portion 10.

  At this time, the convex portion 10 does not protrude from the side surface of the base portion 10a because the fine particle layer 4 is deposited on the tapered surface portion 10b. That is, in the grid pattern 3, the upper line width / lower line width of the convex portion 10 is less than 1.0, and the fine particle layer 4 does not protrude between the convex portions 10, so that light transmitted between the convex portions 10 is transmitted. The transmittance of the substrate 2 can be kept high without being blocked. Moreover, the convex part 10 is provided with predetermined | prescribed height by providing the base 10a. Therefore, the grid pattern 3 has a high contrast.

The grid pattern 3 is appropriately set in processing size and pattern shape in accordance with an intended polarization characteristic (extinction ratio) and a target visible light wavelength region. Specifically, the grid pattern 3 has a pitch P of the convex portions 10 of 100 nm to 250 nm.
Lower width W1 of the convex part 10: 50 nm to 200 nm
Lower width W1 of the convex portion 10 / Pitch P of the convex portion 10: 0.55 or more Height T of the convex portion 10: 20 nm to 200 nm
Taper angle A of the tapered surface portion 10b: 30 ° to 75 °
The upper width W2 of the upper portion of the convex portion 10 and the fine particle layer 4 / the lower width W1 of the convex portion 10 is less than 1.0. The film thickness of the fine particle layer 4 is, for example, 100 nm or less.

[Production Method of Polarizing Element 1]
Next, a method for manufacturing a polarizing element will be described. First, as shown in FIG. 3A, a translucent substrate 2 such as quartz is prepared. Next, as shown in FIG. 3B, a grid pattern 3 is formed on the surface of the substrate 2. As a method of forming the grid pattern 3, for example, a resist mask corresponding to the grid pattern 3 is attached, exposed, developed, and then etched. At this time, after performing anisotropic isotropic etching, isotropic etching is performed, whereby a base portion 10a having a substantially rectangular cross section and a taper in which a pair of tapers are formed at a predetermined angle A on the upper portion of the base portion 10a. Surface portion 10b is formed.

  The taper surface portion 10b is angled by controlling the gas pressure of the etching gas. As will be described later, the tapered surface portion 10b is preferably in an angle range of 35 ° to 70 °. The control of the angling and the gas pressure can experimentally determine the optimum conditions such as the degree of vacuum and the gas flow rate according to the material of the substrate 2 and the type of etching gas.

  As an example of the etching conditions, CF4 is used as the fluorine-based gas, the gas flow rate is 25 sccm, the power is 120 W, the bias is 60 W, and the etching time is 120 seconds. Moreover, the height T of the convex part 10 formed by this is 15-30 nm.

  Next, as shown in FIG. 3C, the fine particle layer 4 is formed on the tapered surface portion 10b. As shown in FIG. 4, the fine particle layer 4 is formed by ion beam sputtering from an oblique direction. In FIG. 4, 21 is a stage on which the substrate 2 is placed, 22 is a target, and 23 is a beam source (ion source).

  In the stage 21, the substrate 2 is arranged so that the lattice direction (longitudinal direction) of the grid pattern 3 is orthogonal to the incident direction of inorganic fine particles such as Al. Further, the stage 21 is inclined at a predetermined angle with respect to the normal direction of the target 22 so that the incident angle of the inorganic fine particles with respect to the grid pattern 3 (the angle formed between the normal of the substrate 2 and the incident direction L of the inorganic fine particles) θ is The fine particle layer 4 is set so as to be formed only on the tapered surface portion 10b according to the height of the base portion 10a and the angle of the tapered surface portion 10b, for example, 87 ° to 60 °. If the incident angle is too small, a large amount of inorganic fine particles are attached not only to the tapered surface portion 10b but also to the skirt portion of the base portion 10a, and the transmittance characteristics deteriorate.

  Ions extracted from the beam source 23 are irradiated to the target 22. The inorganic fine particles knocked out from the target 22 by the irradiation of the ion beam are incident on the surface of the substrate 2 from the oblique direction at a predetermined incident angle θ and adhere to the tapered surface portion 10b.

  Thus, by tilting the substrate 2 with respect to the target 22 and defining the incident direction of the inorganic fine particles, the fine particle layer 4 made of inorganic fine particles can be selectively formed on the tapered surface portion 10 b of the convex portion 10. . As a result, the fine particle layer 4 having shape anisotropy can be distributed in an island shape on the surface of the substrate 2 in a desired fine shape. At this time, the fine particle layer 4 is formed on the tapered surface portion 10b of the convex portion 10 by setting the incident angle θ, for example, 87 ° to 60 °, according to the height of the base portion 10a and the angle of the tapered surface portion 10b. It is formed without protruding to the side of the base portion 10a.

  The fine particle layer 4 may be formed by, for example, an oblique deposition method in addition to the ion beam sputtering method. However, by forming by ion beam sputtering, the energy of incident particles is higher than that of vapor deposition, and the adhesion strength of metal fine particles to the substrate 2 which is important for ensuring device reliability can be improved. . In addition, the material that can be deposited is largely limited by the characteristics of the material such as its vapor pressure. However, since the sputtering method does not have such a limitation, the ion beam sputtering method is advantageous in that the range of selection of the material is widened. .

  The substrate 2 may be provided with an antireflection film (not shown) that suppresses a reflection component with respect to incident light on the surface opposite to the surface on which the grid pattern 3 is formed. The antireflection film may be a general antireflection film material formed by single-layer or multi-layer deposition.

  In the polarizing element 1, a protective layer may be formed on the fine particle layer 4. A general material such as SiO2, Al2O3, MgF2 can be used for the protective layer. These can be thinned by applying general vacuum film formation such as sputtering, vapor phase epitaxy, and vapor deposition, or coating a sol-like substance on the substrate 2 and thermosetting it.

[Effect of polarizing element]
In such a polarizing element 1, the fine particle layer 4 made of an inorganic material formed on the surface of the substrate 2 has an anisotropic shape in the in-plane X and Y directions as shown in FIG. Distributed. These fine particle layers 4 absorb a polarized component having an electromagnetic traveling direction in the major axis direction (Y direction) and transmit a polarized component having an electromagnetic traveling direction in the minor axis direction (X direction).

  Further, in the polarizing element 1, the fine particle layer 4 of the convex portion 10 constituting the grid pattern 3 is deposited on the tapered surface portion 10b and does not protrude from the side surface of the base portion 10a. That is, since the fine particle layer 4 does not protrude between the convex portions 10 in the grid pattern 3, the light transmitted through the convex portions 10 is not blocked, and the transmittance of the substrate 2 can be maintained high.

  Further, since the polarizing element 1 is provided with the grid pattern 3 directly without providing a metal film on the substrate 2, even if a resist pattern is formed by a photolithography technique such as an interference exposure method, pattern collapse or constriction occurs. Therefore, the fine grid pattern 3 can be formed with high accuracy by etching.

  Furthermore, the polarizing element 1 forms the convex part 10 which has the base part 10a and the taper surface part 10b provided in the upper surface of the base part 10a by switching anisotropic etching and isotropic etching. The convex portion 10 has a predetermined height by providing the base portion 10a. Therefore, the polarizing element 1 can form the grid pattern 3 having high contrast.

  Here, FIG. 5 shows the relationship between the height T and the lower width W1 of the convex portion 10 of the grid pattern 3 and the average transmittance of light in the GREEN band (530 to 580 nm) of the polarizing element 1. As shown in FIG. 5, the average transmittance of the polarizing element 1 is increased to about 96% by setting the lower width W1 of the convex portion 10 to 95 nm or more and the height T of the convex portion 10 to 45 nm or more. Can do. In the polarizing element 1 relating to the measurement of the average transmittance shown in FIG. 5, the grid pitch P is 148 nm, the angle of the tapered surface portion 10b of the convex portion 10 is 60 °, the thickness of the inorganic fine particle layer 4 is 20 nm, and the protective layer ( SiO2) is 20 nm.

  Since the polarizing element 1 loses about 4% of the light irradiated on one surface where the convex portion 10 is provided, an antireflection film is formed on the other surface opposite to the convex portion 10 and the loss is 0%. The maximum transmittance is 96%. Therefore, the average transmittance of the polarizing element 1 can be maximized by setting the lower width W1 of the convex portion 10 to 95 nm or more and the height T of the convex portion 10 to 45 nm or more.

  FIG. 6 shows the relationship between the average transmittance of light in the GREEN band (530 to 580 nm) of the polarizing element 1 and the lower width W 1 of the convex portion 10 / the pitch P of the convex portion 10. By setting the lower portion width W1 / convex portion 10 pitch P to 0.55 or more, the average transmittance characteristic can be 94% or more.

  FIG. 7 shows the relationship between the average transmittance of light in the green band (530 to 580 nm) of the polarizing element 1 and the angle A of the tapered surface portion 10 b of the convex portion 10. As shown in FIG. 7, by setting the angle A of the tapered surface portion 10b in the polarizing element 1 shown in FIG. 1 to 35 ° to 70 °, the average transmittance in the GREEN band with a wavelength of 530 to 580 nm is set to 95% or more. be able to.

  In addition, when the convex part with the rectangular cross section was provided without providing the tapered surface part 10b at the tip, the average transmittance remained at 93% under the same conditions. This is because the fine particle layer 4 of the convex portion 10 constituting the grid pattern 3 is deposited on the convex portion having a rectangular cross section, and as a result, the fine particle layer protrudes between the convex portions from the side surface of the convex portion and is transmitted between the convex portions 10. By blocking.

[Moss Eye]
Further, in the polarizing element 1, when the base portion 10 a of the convex portion 10 is formed, a protrusion 11 having a lower profile than the convex portion 10 is formed between the convex portions 10 on the surface of the substrate 2. When the base portion 10 a is formed on the substrate 2, the protruding portion 11 is formed along the convex portion 10 between the convex portions 10 by scraping both sides of the base portion 10 a. FIG. 8 shows an SEM image of the grid pattern 3.

  By forming the protrusions 11, the grid pattern 3 of the polarizing element 1 is regularly formed with a protrusion array including the protrusions 10 and the protrusions 11, thereby forming a moth-eye structure. Accordingly, since the refractive index in the thickness direction of the polarizing element 1 continuously changes, the light that strikes the substrate 2 is hardly reflected and the transmittance can be kept high.

DESCRIPTION OF SYMBOLS 1 Polarizing element, 2 board | substrate, 3 grid pattern, 4 fine particle layer, 10 convex part, 10a base part, 10b taper surface part, 11 protrusion part

Further, the method for manufacturing a polarizing element according to the present invention includes a translucent substrate that is continuous in one in-plane direction of the translucent substrate, and has a base having a rectangular cross section and a predetermined angle formed at the tip of the base A step of forming a grid pattern in which a plurality of convex portions each having a taper surface portion having a taper having a pitch smaller than the wavelength of light in the use band is formed, and inorganic fine particles are applied only to one taper of the taper surface portion. obliquely by laminating, have a forming a fine particle layer that does not protrude from the side surface of the base portion, in the step of forming the grid pattern, when forming the base to the transparent substrate, the This includes forming a ridge that is continuous in parallel with the convex portion formed by cutting both sides of the base portion, and has a lower profile than the convex portion .

Claims (12)

A substrate transparent to the light in the use band;
On the surface of the substrate, a plurality of convex portions continuous in one in-plane direction of the substrate are formed at a pitch smaller than the wavelength of light in the use band, and a grid pattern made of a translucent material,
The convex portion comprises a base having a rectangular cross section and a tapered surface formed at the tip of the base, and a fine particle layer made of an inorganic material is laminated on at least one surface of the tapered surface,
The polarizing element does not protrude from the side surface of the base portion.   2. The polarizing element according to claim 1, wherein the grid pattern has a ridge portion that is lower in height than the convex portion that is continuous in parallel with the convex portion and has a moth-eye structure between the convex portions.   The polarizing element according to claim 1, wherein the translucent substrate and the grid pattern are formed of an inorganic material.   The polarizing element according to claim 3, wherein the translucent substrate and the grid pattern are formed of quartz or sapphire.   The polarizing element according to any one of claims 1 to 4, wherein a ratio of a width of the convex portion to a pitch of the convex portion is 0.55 or more.   The polarizing element according to claim 1, wherein an angle of the tapered surface portion is 30 to 75 degrees.   The width of the convex portion is 50 nm to 200 nm, the height of the convex portion is 20 nm to 200 nm, the angle of the tapered surface portion is 30 degrees to 75 degrees, and the pitch of the convex portions is 100 nm to 250 nm. The polarizing element according to item 1.   The said board | substrate is provided with the antireflection film which suppresses the reflective component with respect to incident light in the surface on the opposite side to the surface in which the said grid pattern was formed. Polarizing element. Convex portions that are continuous with the translucent substrate in one in-plane direction of the translucent substrate and are formed of a base portion having a rectangular cross section and a tapered surface portion formed at the tip of the base portion are longer than the wavelength of light in the use band. Forming a plurality of grid patterns formed at a small pitch;
And a step of laminating inorganic fine particles on the tapered surface portion from an oblique direction to form a fine particle layer that does not protrude from the side surface of the base portion.   The method for manufacturing a polarizing element according to claim 9, wherein the incident angle of the inorganic fine particles is set so that the fine particle layer is formed only on the tapered surface portion according to the height of the base portion and the angle of the tapered surface portion.   The method for manufacturing a polarizing element according to claim 9, wherein the grid pattern has a ridge portion that is lower in height than the convex portion that is continuous in parallel with the convex portion between the convex portions, and a moth-eye structure is formed. .   The method for manufacturing a polarizing element according to claim 9, wherein the protrusion and the protrusion are formed by using anisotropic etching and isotropic etching in stages.

Images